Global study highlights critical challenges facing lake ecosystems worldwide

Lakes are considered the lifeblood of numerous ecosystems worldwide and one recent study has underscored the urgent need for coordinated action to address the issues jeopardising the health of lakes across the world.

Co-authored by a global research team including Griffith University academics, the study examined the various ailments impacting nearly 21 million lakes around the world that are greater than one hectare in area.
 
Griffith University Australian Rivers Institute Director and study co-author Professor David Hamilton said the ramifications of neglecting lake health are profound.

“Lakes, in their varied sizes, shapes, and hues, are vital storytellers of geological evolution and environmental change,” he said. 

“However, the health of these bodies of water is under siege from a plethora of ailments, including thermal, circulatory, respiratory, nutritional, and metabolic challenges, as well as infections and pollution.

“Without timely intervention and preventative measures, these issues could escalate into chronic conditions, imperiling essential ecosystem services that millions of people rely upon.”

Hamilton stressed the necessity of applying strategies akin to human healthcare to lake management, including early identification, regular screening and remediation efforts.

“Lakes need to be recognised as living systems that can suffer from a large variety of health issues, which are similar in many ways to human health issues,” he said.

“Despite increasing preventative and treatment efforts in many countries, evidence for substantial improvement in the overall global lake health status remains elusive.
 
“Thus, there is a high risk that more and more lake health issues will become chronic and difficult to treat.”

Lake ailments

Australia has around 11,400 lakes with the majority being salty due to high rates of evaporation, alongside other areas such as parts of Africa and Central Asia, which evaporate much more water than they receive.

Of concern among the findings was the widespread phenomenon of lake drying, exacerbated by human stressors and climate change. This is also impacting the availability of water stored in artificial reservoirs and dams.
 
About 115,000 lakes globally are evaporating at an alarming rate, posing risks to the more than 153 million people who reside nearby. Hamilton said rising temperatures are also significantly impacting many lakes' natural mixing regimes.

“Two of the issues are thermal and circulatory changes in lakes, which directly relate to the effects of climate change. Lakes are sensitive to warming, but deep lakes also undergo critical circulations that correspond to different seasons and temperatures,” he said.
 
“Typically, in winter, a lake will mix fully – the cooler air and water surface temperatures create cooler and denser water, which sinks to the bottom of the lake. The lake naturally circulates, a process that is critical to replenish dissolved oxygen in bottom waters.
 
“With a warming climate, that seasonal mixing has either disappeared, or it has become shorter and shorter. This results in a reduced period when oxygen is being replenished in the bottom waters.
 
“This mixing period is really critical, it is essential to sustain the oxygen within the water, but also to sustain the fish, and the overall ecological balance of the lake.”
 
Hamilton said climate change is already playing a big role now in terms of how lakes around the world are behaving.
 
“Lakes have traditionally been categorised according to the way that they mix seasonally. But with climate change, those categories have been altered and sometimes broken down completely. For example, loss of ice cover in many lakes makes a huge difference to the way that they function,” he said.
 
“These health issues with lakes pose a huge risk to human health. We hear a lot about water security, which is often thought of in terms of quantity, but there is a complementary aspect of water quality as well.
 
“For example, if a lake or dam is full of cyanobacteria or chemical residuals, we have less water available to meet drinking water requirements.”

Health checks

One of the things that became evident in the study is the disparity among different countries in terms of how to assess the health of lakes: “What we would like to see is a more uniform approach to assessing the health of lakes globally,” Hamilton said.
 
In terms of how to approach health checks for lakes all around the world, Hamilton said remote sensing is making a big difference.
 
“There is no way we can possibly monitor all of the of the lakes on Earth, but remote sensing does offer the opportunity to conduct comparative assessments across many lakes. High-frequency sensors are also very useful.
 
“Chlorophyll is an indicator of algal concentrations, and we can therefore track algae and other indicators like dissolved oxygen using high-frequency sensors. They sit in the water and can give us real-time readings, which allows us to be much more responsive.”
 
Hamilton said the most significant issue facing monitoring efforts is resourcing.

“We have the technology, but we are not yet devoting the analytical capability to be able to interrogate and understand what the data is telling us. It’s resourcing that's the challenge,” he said.
 
“We are in the era of the ‘data deluge’. AI and machine learning certainly offer big opportunities in cases like this, but it all needs to be joined up.”
 
To avert an ecological catastrophe, the study advocated for a comprehensive approach encompassing improved wastewater treatment, climate mitigation, prevention of non-native species introductions and curbing chemical pollution.
 
“Many lakes act as sentinels, or indicators of what is occurring in the broader catchment. Looking after lake ecosystems means not just what occurs in the lake itself, but also what occurs in the catchment,” Hamilton said.
 
“If we are looking after the catchment, we will benefit from having good water quality in lakes and dams. If we can ensure a healthy lake ecosystem, we will be less likely to have to manage algal blooms or loss of oxygen that are responses to poorly managed water catchments.”